Each of Patent Documents 1, 2 and Non-patent document 1 discloses a nitride-based semiconductor light-emitting device that includes two nitride semiconductor layers and an active layer. The active layer has an InGaN single-quantum-well structure and is disposed between the two nitride semiconductor layers. The two nitride semiconductor layers and the active layer are disposed on a GaN substrate. The nitride semiconductor light-emitting device described in Patent Document 1 includes an n-type cladding layer of n-type nitride semiconductor, a p-type cladding layer of p-type nitride semiconductor, and an active layer of nitride semiconductor containing at least indium. The active layer is disposed between the n-type cladding layer and the p-type cladding layer. The n-type cladding layer and the p-type cladding layer have smaller coefficients of thermal expansion compared to the active layer. The active layer has a single-quantum-well structure (or multiple-quantum-well structure) and emits light having lower energy than inherent band gap energy of the nitride semiconductor of the active layer. The LED described in Patent Document 2 has an InGaN single-quantum-well structure on the {11-22} plane of a GaN substrate. The nitride semiconductor laser device described in Patent Document 3 includes a nitride semiconductor layer and an active layer. The semiconductor layer includes a layer of AlGaN. The active layer includes a layer of InGaN and is deposited on the nitride semiconductor layer. The active layer includes a single-quantum-well structure (or multiple-quantum-well structure). The growth surface of the nitride semiconductor layer tilts from a c-plane of the GaN substrate.